Communication system



www wal INVENTOR affari.

HIS ATTORNEY.

Paul

A v WNQ NN www M NN lrs llllll.

Feb. 28, 1950 Filed Jne 25, 194e IIL N1M|| I E @um E s Feb. 28, 1950 P. N. BossART COMMUNICATION SYSTEM 3 Sheets-Sheet 2 Filed June 25, 1946 E Fmr@ Feb. 28, 1950 P. N. BossART COMMUNICATION SYSTEM 5 Sheets-Sheet 5 Filed June 25, 1946 .,r. Y wf 0 M N w m W w mma-m p W m wm w E E w 1 v u @www a Mw ww. mm fkk mm R n. .f m Mm gj N a .n Q 14 m b QU .MMV Mmm! A, E W IH IH Mw E E @MH n@ communicationsystem.

Patented Feb. 28, 1950 UNITED STATES PATEll-SITl OFFICE y CQMMUNICATION: SY STEM .Pal N..Bossart,CheswickgPaW assigner to. The UnionY Switch &' Signa1 Company,fSvvissvale,A Pa., a` corporation flof'Pennsylvana l Application June 25, 1946,seria1 No. 679,099

. My invention relates. to-communication sys` tems,A and more particularly toinductive carrier communication `'systems for vehicles, operating over. a given trackvvay.` "i One of! the purposes of a communication systenrfor vehicles operating over a giventrackway is to provide communication between Va terminal station and the vehicles en route. Under .such circumstancesthe requiredrange of transmission `varies greatly. For example, in railwaytrain lcommunicationsystems the range betweena ter- .minal vstation and a train carried station will range of transmission of the energyorignally supplied may be insuiiicient to reach remote vehicles. l, j

Accordingly, a feature ofs myinvention is the provision of novel and improved means vto extend the range .of transmission of aninductivecarrier Anotherfeature of my invention is ,th'epro- Y vision of communication"I equipment .of ythel.type

herein .involved incorporating improvedxmeans to provide" duplexl ortvvo waygservice' on aplurality odi'erent frequency channels simultaneously.

Still' .another feature of. my inventionis the f. provision. foi" inductive i carrier ,communication .systems incorporating .novel andimproved repeater equipment whereby aterminal stationat..

one. end of..v ana-extended trackway. vcan communicate with. a vehicle enroute.

Again, a feature of myinventionaisthe.;pr.o

- .vision-:of: improved .means Wherewth 'carriericommunication: energy: is: amplied and. `repeated at' locationsalong Ya trackway.' by' transferring-r the ,energyA from. transverse v" to. 'longitudinal'. circuits ofia pair of line wires and vice` versaalternately.

vAmore specific' feature of my `invention is the `I provision of carrier inductive railvvaytraincommunication systelns incorpz iratingVM improved whereby' terminal stations.. one attach',

.auf

terminal stations.,

invention will appear as the 10;

,ofi the. diyisionwith .an...overl'apped stretch Where Vwherewithtrains of a division can` communicate with each other as well as keeping in touch with Other features objects and' advantages ofmy specication progresses. 4

The foregoing featuresobjects and advantages of my invention I attain through thev provision fof longitudinal andltransverse circuits of a pair of*r line wires extending along a trackway over which vehicles operate, together with sectionaliz'- ing and repeater means .at preselected points along the trackway todetermine the limits of the. longitudinal and' transverse circuits.` VThe xtwo ,line wires in jparallel, the distributed capacitance and conductance of theline wires to ground andthe ground path form a so-called longitudinal circuitk and such aA circuit will be thus` calledY throughout the present, specication andcl'aims. The line Wires when used in series forma metallic" or str-called transverse circuit-and in the specification and claims I shall` use-fthe term transverse *circuity to" designate the circuit formedbythe line wires in series. Y v

f The; twolinewires are mounted parallelto and Vreasonablyl clos to the trackway' andthe longitudinal circuit formed by the line wires is Y"inductively'associated"with vehicle carried elements or circuits. Waysidegor't'erminal station equipment isconnected orv coupled to theline wires to send and receivev the communication` -Y current' therethrough. The eldf setv up from' the ltransversel circuit' is 40" db. or more` below that setup" from alongitudinal circuit sothata great deal' more powerm'ay be' ffed'linto a transverse .wci'rcuitwithout exceeding theso-called govern- `ment low power rule limiting the field to 1'5 microvolts per meter at a distance normal to the Aline of "onef electrical' radian. The longitudinal balance of'a pair' ofY line wires is usually' 35i-to 40 db. or better;r so that repeater gain uptothis 'amountj'may beused-:without resulting inv feed back'suiiicient to cause instability. vIfline circuit A attenuation isaboutl db. permile, then repeaters can be1spaced25 to 30 miles and the range of transmissionl extended.

Each repeat r'reluipmentV here provided includes an.ajimollifi-` 'nd a iilter and the; several Vare corn'iecteilztoy thepair necessary to transienthje'fcommunication. energy from the transverse-l tothe iilter and amplifier that vides an overlap of 40 miles in which either ter- V minal station can communicate withairain.

The purpose of such an overlap is that if a con-.1, versation starts, say, 95 miles from the terminal at the east end of the division with a westbound` train, the conversation mightvlast f or many minutes so that at the time itwas completed the train might be 115 miles from the .terminal. Without such an overlap there would be danger lof interrupting the communication between a train and a terminal station by the train moving out of the range of that station before communication can be established with the other station.

`,'Ijwo way service is provided between wayside or terminal stations and vehicles en route on any desired number of communication channels sl- .:multaneously through the use of different car- 1riers and lters. In one embodiment of the invention each two way conversation is effected of a high group of carrier frequencies for transmission from the vehicles to the terminal stations. l

In another embodiment of the invention, one

. `group of carrier frequencies is used for all trans- ,missions from east to west along a trackway A, and another group of carrier frequencies is used for all transmissions from west to east. In this latter scheme, an operator on board a train wish- .ing to talk to the west would use a carrier frequency in the west group and if he wishes to talk-east he would use a carrier frequency inthe east group. The reply to a message will be effected by using a frequencyV of the other group.

At a terminal the choice of the group of frequencies to be used will depend upon the terminal beingat the east or west end of the divi- Each repeater equipment is arranged with two l,circuit channels, one channel including a filter and an amplifier disposed to pass the carrier frequency used for transmission in one direction and the other channel including a filter and an .amplifier disposed'to pass the carrier frequency used for transmissionin the other direction. That is, each circuit channel of a repeater equipment is made directional in character bythe make up the circuit channel.

I shall describe two forms-of apparatus embodying my invention, and shall then point out -the novel features thereof in claims.

In the accompanying drawings,` Figs. 1a and lb when rplaced end to end with Figjla at the --station to trains and a second or high group of carrier frequencies. are fused, for transmission from trains to the terminal stations.y Eig. 2 isav diagrammatic view 'showing a form of apparatus embodying my invention when used in a railway vtrain communication system and wherewith duplex service is obtained by using a rst carrier frequency or group of frequencies for all transmissions east and a second carrier frequency or group of frequencies for all transmissions west.

In each of the differentviews .like reference characters are used todesignate ."similar parts.

It isy understood that `my invention is not limited to railway train communication systems and this one application illustrates the many places the equipment is useful.

.Referring toFigs. 1a and lb, the reference character RT designates a railway track extendf ing betweentwo divisional terminals E and W. `Such a division would be of the customary length and to aid in the understanding of the inven- *tion` I 'shall assume the division to include 120 miles of track. The railway may be a single track line or the trackRT may be one track of 4 al multiple track railway. I shall furtherv assume lthat the trackRT is an eastbound track ofjj'a multiple track line and the several trains designated VI, V2, V3 and V4 are eastbound en route rover track RT, and each of vwhich trains hasuat least one vehicle provided with communication equipment. q l. The reference characters LI and L2 designate afpair of line wires extending along the railway. Theseline wires would'be carried on the usual pole line and would extend substantially parallel Vto and reasonably close to the trackRT. That is, the line wires Ll and L2 extend continuously throughout the territory covered by the communi- ',.cation system and are at all times within effective Iinductive range of the track. This pair of llnel wires may be used in existing telegraph or similar service and are used for train com munication asan additional service without interference with their present use. The line wires ULI. and L2 may be of course installed vfor train communication use only. It is `to beobserved that the same pole Iline may .carry additional line wires, such as line wiresLS,v and L4, fragments of which are shown adjacent terminals E'andW.

. yAs will .be pointed out as the specification prol gresses, the line wires LI and L2 are sectionalized and arranged in transverse and longitudinal circuits for conveying the train communication current along therailway but are retained as a series circuit for their present use. v

The east terminal station E and the west terminal station W and each train` operating over the division are provided with two way conjmunication `equipment comprising transmitting apparatus andv receiving apparatus which are shown conventionally for the sake of. simplicity since the specific structure. of .these apparatuses forms no part of my invention.

As stated hereinbefore, in the embodiment'of the invention disclosed in Figs. fla' and' 1b; aiflrst or low group fofcarrier frequencies are provided for' transmission from terminal stations to trains and a second or high group of carrier frequencies `are provided for transmission fromitrainsy to terminal stations, so that a plurality of conversations can be carried on simultaneously. I shall assume for illustration that the low group comprisescarriers Cl and C2 of frequencies ,fl and f2, respectively, and the high group comprises .carriers .C3 and C4 of frequencies ,f3 and.f4,r`e '.spectively.Thusfinthe case here used'frillustration, two; two-way or duplex yconversatir'is 'can' be carried on simultaneously,'one "conversa- Stimm-.186

tionfusing,4 say', carriersfJC I? and andf the other vusing carriers: C2 1 and" CA. Itzi'stohe understood Ithat:` each'` group'. of carriers: can include;v addi.- tional': carriers if. additional conversations: are needed..

4Under the, `carrier `groups :heretzused for-'illustra'- tion, the; terminal; station: E isz. provided with transmitting apparatus which comprises two :transmitters TCI and 'TC2;for. sending on .the 1carriers 1C I f and` C2, respectively; andwitharecey- .ing apparatus which comprises two receivers -RCBfanci RC4 for receiving onithe carriers-C31 and C4, respectively. Such-transmittersandreceivers aswell as4 other transmitters and. receivers re;-

, erred to hereinafter may begilorvr example, similar' @to those disclosed in` Letters Patent ofthe-.United States No, 2,064,639,l granted. December:t v 1,936, to L. D. Whitelock et` all, lfor. Communicating systems, or Atcx the arrangements disclosed in Amy ,copending application `for Letters Patent of the ,Unite-d States, Serial. No. 575,311, `iiled- January :3(15'19415, noW-Patent.No..2,484,680., dated October :1l-11;, 19e-9,. for Railway train,Y communicationsystems. i

- -z'lhey transmitters TCI and' 'IC2in` parallel are -connected'across-.the line-wires LI1andL2 through ,a directional band pass filter BDE andblocking .capacitorsV I I: and I2.. The-filter LDB! at station E las, well as all other lters identifiediby the refr-:rencecharacter` LLDF;` tot bev-referred to herey inaiter,` are proportioned to i pass t Y a frequency 'hand including the ilowcarrier group-CI and C2 `and to suppress irequenciesoutside ofsuchgroup. "Ihewcapacitors II and |21 would pass all carrier frequencies here used butfblocle direct` current t and -very lowl frequencyy currents usedl intelegraph an'dpthercircuits "completed through the line wires LI and L2. Similarly, the receivers gRCSf and RC4 at sta-tion E .in 'parallel aref-conl,nected across the line wires LI and L2y through: a directional bandv pass filter HDFxand the capacitors' I I` and. I2. `'The 'lilter HDF atfstation E, :as Well as all'oth'er similar filters referredvtof here- .inafterg'are proportioned to pass the 'frequency band including the high groupeofncarriers-C3 and ,Cllffand to suppress frequenciesoutside:- of such Igroup. In other: words-the lter LDF servesto A pass -only the low group of carrier. frequencies sent out from the terminal station E `and-.the ilter. HDF- Serves to'ipass only-the-highgroup of carrier frequencies receivedat'terminal-.E*, and 4to suchY extent theseVlters-aredirectional.

The terminal 'station is :providedwith .similar f'equipment,l the; 'transrnitting.,Il apparatus includ.-

ing.V two transmitters-,fTGl' and: TG2...which are connected inparallelacrossthe; line wires LI- and :L2 through` a i directional, band passe filter. LDF and,l blocking capacitors I 3l andv |14, andtheY receivine apparatus includingtwo receivers `"RC3 and RC4 l which*y 4arefconnected in parallel 4across the: line Wires through y a-l directional .bandi pass Aiilter-H/ZDF and the blockingI capacitors I3 and 'lgt.' It is `to be seen, therefore,v thatweach terminal station. E and'` Wl isfecuipped'to send on 'feitherf'offthe'low group. carriers CI and C2 and:

to receive on either of the high group carriers -Ctf and C4, andxeacheterminal.equipmentl'is f connected to the linewires in a1 transverse circuit. The communication Aequipment of each train isl similar' to that, vprovided at .theterniinal` sta-1vl tions, except vas to; the' tuning. Taking train VI, 4'for example, itsf equipment- `comprises-r,transmit- *t'ng'I/-apparatus' shown:conventionailyat :TAV and ceiving apparatus shown conventioneuilly:s at RA.

The taiismittingff apparatus 'TA ""Would; include l 6 twofftransmitters t capable of 'sendingl 'ong the care rier :frequency: C3 and' C4, respectively,l andthereceiving apparatusT RA would 'include two re:- ceiversv capable offreceiving the carrier nfrequency C I -f and C2, respectively; i

Stiltreferringwto trainVI, its receiving'. and transmittingapparatuses arer connected: to circuit. elements which are electrically coupled; to the trackway transmitting channel. The zreceivingffapparatus is connected to anali' core coil Im and the; transmitting apparatus:l TA is con.- nectedz'tor va sending circuit which includes., two spaced pairs of wheels I5 and I6 of the train. "The coil. l0 is mounted for inductive; relationfwith thefrtrack. rails? and conductors paralleling the rails? Current. supplied by the transmitting ap,- vparatusTli,.flows in,` therails between theftwo pairs: of wheels. I5 and Hfand the voltage drop developed?, across this length of rail causescur.- renttoi flow in. the rails each side of the train and.' the distributed rail to ground impedance and energyfis `transferred tothe line wires LI` and LZ'in multiple due to the distributed inductance betweentheline wires and the rails. Such trans- 'erofienergyto and Zfrom train carried apparatus and, the trackway transmitting channel; including' the:t longitudinal circuiti of the linewires'r is fullyexplainedinmy Letters- Patent of the United JStatesNo*2,0f5ii2, granted December 15,11936, 'forRailway traini'ccmmunication systems. `Thus both `the receivingv apparatus RA and thel transmitting apparatus TA oftrain VI are inductively associated with the longitudinal. circuit ofthe linewi-res LI and L2. Each of the other trains is .provided with communication apparatus` simi.- lar-.to that of train VI'.

Repeater equipment is providedat a plurality of preselectedy points through the division to :exh tend the range of transmission and thereby pro.- ,vid-e communication between the terminal stations and-a train at any point along the railway. On the assumptionthat-the terminal, stations Eand W are .120 miles `apart and service.. is desired from the east terminal El to all trainswithin 8.0 miles ofy that terminal and from. the west terminal W sto alltrains within `miles of that terminal, repeater points Allan-d BE 20 and 4;() miles, respectively, from terminal -.E; repeater points AWl and BW 20 and Li0 miles, respectively, from terminaly W; and. a.. repeater' point` ALmid- 4way''between thev points :BW and BF,are` provided. With thisv arrangement an .overlap .of 40, miles in which either terminal can talk to.,.a train isprovided,` the purpose of such overlap being explained. hereinbefcre. While, a :specific spacing of `therepeater pointsis showninithe drawings, it is understood thatthe, invention.. is not-limited" to this one` spacing and other. spacings canhe; used. I .A f Each l, repeater equipment includes l two. r separateA channels, one for repeating the energy trans'` .mitted from the terminal .stations-to thetrans and `thee other for repeating the energy transmitted from the trains to the4 terminal stations. Locking'at: the repeater point AE, for example, the repeater equipment includes ia rst circuit channel` LC and :a second circuit channel I-IC. The channelLC includes low directional band pass filters l1 and IBuand anamplifler i8; The filters I1 and I9- are LDF filters proportioned to `rmgss the low carrier'group. The ampliiervt Wouldzbe of. standard arrangement disposed with its: inputfcnnnected', to; thezlcutputsof thefltcr I'I- :and-i itsiroutputzfccnne ctecl-4 tothe; input cfzthe filter/f 19:1 Thus* thisrcircuit: channel LCniSisdsand vehicle stations east.

posedfto pass only'energy of the low carrier group from the station E to trains west of the repeater point AE. Similarly, the second circuit channel HC includes high directional band pass l- 'circuit to the longitudinal circuit and vice versa, -s'uch connections being explained more fully as the operation of the apparatus is described.

In describing the operation of the apparatus of Figs. 1a and 1b, I shall rst assume that the Ioperator at the east terminal E desires to talk to some train Within 80 miles of that terminal station. I shall further assume that this conversation between the station E and the' train lis'eiected by the use of carrier CI. The operator at station E on selecting the transmitter TCI causes energy to be applied to the line wire in the transverse circuit and the energy flows in the transverse circuit to the first repeater point AE. This energy, attentuated by the line Adrop of miles of the line circuit is taken off the transverse circuit by wires 8 and 9 and is passed by the first circuit channel LC of the repeater equipment. After being amplified the energy is applied to the line wires LI and L2 in a longitudinal circuit, the connection being completed between ground electrode and the junction terminal of capacitors 23 and 24 connected in series across the line wires. The outgoing carrier energy thus applied to the longitudinal circuit at repeater point AE will flow both east and west and will be available to inductively influence the receiving apparatus of v train V3 en route somewhere between repeater points AE and BE and also the receiving apparatus of train V4 en route somewhere between terminal E and the repeater point AE.

The attentuated energy is taken off the longitudinal circuit at the repeater point BE and is passed through the circuit channel including a low carrier directional filter 26, amplier 2'|y and a low carrier directional lter 28. After ampli'- cation the output` is passed to a transverse circuit of the line wires through wiresI 29 and 3|).

, At the repeater point BE a low pass lter 3| is interposed in the line wire and proportioned 'to pass direct current and very low frequency currents, such als are used in the telegraph, voice 'frequency telephone, and other circuits completed through the line wires but to block the carrier frequency energy here used for communication. The purpose of the low pass lter 3| is toppre- `vent the repeater equipment BE receiving comvmunication energy from wayside stations west The twice amplified energy 1S transmitted from the repeater point BE over the transverse circuit to the repeater point AL Where it is taken off by wires 32 and 33 and passed through a low directional filter 34 to the input of amplier 35. After amplification the energy passes through another low directional filterA '36 land is ,supf-plied to a longitudinal circuit through the con- `nection between ground andthejunction ter yminal of capacitors 3'! and 38 connected in series across the line wires. Since a strong inductive eld is set up by the energy in the longitudinal circuit the train V2 operating somewhere between repeater points AL and BW will receive the energy for operatingvthe corresponding receiver. Also any train between the repeater points AL and BE will pick up the energy. It

'is to be seen therefore that the energy sent out from the transmitter TCI at terminal station E is available on a longitudinal circuit for reccption by trains at all points within 80 miles of `the terminal E. The operator could have selected transmitter TC2 and the transmission of the energy would be in a similar manner.A

Furthermore, both transmitters TCI and TG2 could have been used simultaneously for sending two conversations if desired.

Aductively influencing the receiving apparatus of a train, such as train VI, somewhere between the point AW and terminal W. Also, anytrain operating between repeater point AW and the next repeater point BW will pick up the energy. At repeater point BW energy from the longitudinalcircuit is passed through a first circuit channel including lowdirectional lter 42, amplifier 43 and low directional lter 44 to a transverse circuit of the line wires. i

At repeater point AL the energy is taken off the transverse circuit by wires 32 and 33 land passed by the rst circuit channel including low directional lter 34, amplier 35 and low directional filter 36 and applied to the longitudinal circuit of the line wires. The energy thus aplplied to' the'longitudinal circuit becomes available to influence the receiving apparatus of train V2 between repeater points BW and AL and any other train operating between the points AL and BE.

At the repeater point BW a low pass filterl 45 is interposed in the line wires similar to the low pass lter 3| at the point BE, lter 45 serving for 'the same lpurpose as the lter 3|.

Itis to be' pointed out that the equipment at "repeater point-BW blocks further transmission to the west of the energy sent out from station E and the equipment at repeater point BE blocks .further transmission to the east of the energy sent out from station W.

It follows that the operator at either terminal station W or E can transmit communication energy to any train within 80 miles of the station,

' and any train, such as train V2, operating through the 40 miles between' repeater points BW and BE can receive communication energy from either i station W or E.

In describing transmission from trains to terminal stations, 'I shall iirst take up the case of train V3 transmitting to station E. The operathe longitudinal circuit .of 'the line'fwires, .directo the` inductive relationshippf the; sending circuit` ofwtrain 1V3w-itnthe line wires. Energywthus caused. toxfloW/in the .longitudinal .circuitwill b e passed .bythe secondchaimel I-IGatfthe repeater point `AE and .the amplified 'energywillibe .applied to` the -transverse `circuit of` the :line -wiresi energy Athus appliedto the transverse acircuitds passed `by the HDF `directional lterx'rll atfstation' E and..'appliedg.to tl1e freceivergRQS.

Similarly, energy .ica-n be. -transmitedfromzthe The train-ivd .to the :station E. .the yoperatoron fthe: traingVd conditioning .the .transmittingaapparatus tonpplyfto the sending circuit vcurrentioiltnecar rier C3, and this current A.uilljbe`t.1ansferreii to' the `inductive vrelation ship 'spetween fitilegzsending circuitof the train-.and the .line wires; Tnecurf rent .from the ;longitudirral .;circ uit Millfpapassed `15 the floneitudnaleircuit of the linewiresziduefto Channel HC. to the transversecircuitrand: thence f,

passedgpy the flfter 1.46; ,tov .the ,cor-responding. re-

ceiver RC3 at station E'.

Transmission from tra-infin to-lootntl'leterrnil nal stations is effected .insmultipla With .the

transmitting apparatuson -train 'V2 conditioned 1 d uctvelyrtransterred to the longitudinal ein it of .the f-linefwires. At repeater; vpoint TAL. theeng Grey tile.: longitudinal .circuit is passati` tlfirouahrthe` Second channel. .inoludingnltert f.

amolier 4B and .filter flauto. .the trainmersa.eir-

cuit. Bartofthefenerey ofthe transverseeircuit nous -tQ- repeater pontBE where it is .taker-.1 oi by Wires 29 and 30,an d passed :throng-M thescond.

52to the longitudinal circuitfeast of'rthe repeater point BE, At the repeater point .thsnel'g'y L is .transferred from .the longitudinal 4circuit tov the Y transversegcircuit throughthief econd channel HC. and the encres' from. thetransterse circuit i is .applicato the receiuingfapparatusat the staff cluding filter 53, amplifier Seandltet 5.5430 ith@ longitudinal -circuitwest or the ipoint..BW. .At repeater Apoint AW'- .the .energy is taken. 1ongitudinal,. circuit and passed through tlaeysec ondychannel including ,lter-.SQ-amplier .51 tand filter 5,8 tothe transverse circuit. AtstatiQnW the .energyA from thetran.si/er.se.` circuit .is 'applied nthroughv a high .carrier directional yltei".V 58 to 55 hat the corresponding receiverfRGBfof station@ .It follows from the foregoing; description theapparatusof Figs. 1a and 1b has thefadvantages of providing a plunalityof different twoway conversations simultaneously vbetweentine .terminalstations yand the ftrains en route :each-termi nal station beingable totalk with all .trains opera` ating-inra predetermined adjacent-portionfof-.the j 10 increase the timp'edanceaof thei-linawires to the flow of current invtlleflongitudinal circutbut inf. troduces only la low resistance `to a transverse, circuit. Inv theacase `of parallel line `Wires, such)- as the linerwires LSvandLll, alongitudinal choke coil 6.2 rwomdipreferably ce i.ised'to avoid'transmission to fthe yeast of the :station E, due to :the distributed capacitance and inductanceabetweenf vtire-line `Wires fLi-andvLZ and tneother Wires .10.

on 4tine samefpoiezlineif Similarly, a low `pass lter 63 and choke coils et and jare providedattthe :termi-nalstation W. With the line wires. LI and. L2 thusliisolatediatzeach terminal station I?` and W1, communieation service can be furnished over .theline wiresilii and"L2 eastof station-E and t'vesty of. station IW 'by :providing equipment similar"toftlia't showinn'n Figala and 1b for the.,

. additional territory.

division of the railway. Also tl'iatftor.apr-ese le cted-overlap portion `of the ,divisori corrversations with trains .andeither station; arel permitted.;

coil 6l are interposed in the .line Wires Iul- :and

L2@ tojisolate tlf-1e communication from bein scarf.

rieaeasr or that station. @hesiter su is pir portioned topass direct currentandtnelowgrre quency. .currents fused fin fthe. present telegraph,

At station E a low pass lter 11:10 and-.afchoke Fig. l2 `shows an embodimentv of the :invention which-:uses one carrier frequency or a groupfot carriernfrequencies for tall transmissions ,to-the; Westand another carrier frequency orl vanother' groupof irequenciesior all-transmissions to theL east. v

:In Fig. 2, a pair of line Wires Ll `andLr extend alonganeastbound vtraclrlir'.of a railwayhaving arr-.east rterminalstation Etfand 'a rwest termini. stationlW,xthe.sarne as inFigs, vla and` 1b. I shallf assume that'fthe ,distancezbetween stations E and vWlof Fig;r.2 is suclrthat repeater .pointsCandf D .and .transfer .point CD. are; resul-red. In this arrangement', `in l'order .to prevent tworepeater equipments @simultaneously.repeating :the same communicationsenergy.: it iis-necessary-.to intery posefrinthe :linea/iles .low pass filters lili` and-itl# at thesrepeater' points .Czarid D, A respectivelihas f. well as` lowy pass-filters arand 63' at 4the terminal' stations.v `Alsoycoils. similar to the choke' coils-@61, .65, 62 .fand 6.4. oi Figs. lot-and flb would' preferably he rprovidedatthe stations and atfthe. repeater points Gand yD=of Fig. 2. f .v

` Atthe term-inalstation the transmittin-gapparatus `includes atransmitter TW and themes ceivling. apparatus includes ia 'receiver RE,..tl1 e transmitterfTW andthe 4receiver RE in multiple-l beingf `connectedftotheIlnewwires L! 'and L2 axlongitudinal circuit... The transmitter T'Wfyisr, capable of` supplying k.commu'nication current of a west Vcarrier frequencywiand .the receiver. RE fis responsive tov communication current ofn an east-:carrier frequency fe. Filters WF-and EF Vat .stationE `are directional band passgfiltrs proportionedltopass` carrier frequencies fw andiv fe, respectively. That is, lter EF is a directional-l lteij 'for transnfrission 'tof the `leastv and filter;` WEF is AaLdirerational 'fiilterftorf the current `transmit-.ted to the-West. 3 1 'L Similarly, tt-1e -terrninal s l tion is provided: witlia transmitter? .capalle'A of' supplying: :ou -f ren-t of thefeasts carrieiwrrequenoy `fe'andiaref.. ceiverRW responsiverto vthe West v.carrier ire-1f queificy fw; ASand @the @transmitter TE and i receiver? l RW infmultiplev are conri'ected'.A` to the "longitudi-.l nali circuit of the :'linef'W-iiesj 1a .directional band i pass filter EF "beinginterposed` in the connece'. tion` for the transmitter and a .directional 1 lt'er Wi` being #interposed =inr the. connectionffor l IGBCGV 1 N! :wi Fig; 2f each: trai-n is-protidedl with transrni-t--l i ting apparatus Triliand receiving v anparatus:BM whicnarle connected .torcircuit .elements indu@- tivelynassociatedz withothe longitudinal? circuiti-of e the line Wires the sameiasfinFigs. la andsrlbn The transmitting apparatus .EFM wouldjnrefetably include-two transmitters. ionecarableot;

supplying a carrier current of the frequency fe' for transmission to the east and the other capable of supplying a carrier frequency fw for transmission to the west. Likewise, the receiving apparatus would include at least two receivers, one responsive tothe east carrier frequency fe and one responsive to the west carrier frequency fw.

In the case a plurality of duplex conversations are desired, then a group of'carrier frequencies for transmission to the east would be provided and a corresponding but different group of carrier frequencies for transmission to the west would be provided, and the equipments .at the terminal stations and on lthe trains would include additional transmitters and receivers, there being an individual transmitter and receiver for each carrier used. s A

It is believed that the apparatus at the repeater points C and D, and transfer point CD will best be understood lby a description of the operation of the apparatus, and in describing the operation of the apparatus of Fig. 2, I shall rst assume that communication is desired between the terminal station E and train 68 operating somewhere between terminal W and the repeater point D. The operator at terminal E would` energize the transmitter TW to. supply communi. cation current of the carrier frequency fw to the longitudinal circuit at station E. The energtl is transmitted over the longitudinal circuit to repeater point C where it is passed through a circuit channel including a west directional iilter 69, amplifier 18 and a second west directional filter 1|. The energy thus amplified is applied to the transverse circuit extending west of the repeater point C. This energy is then transmitted over the transverse circuit to the repeater point D where lt is passed through a circuit channel including west directional filter 12, amplifier 13 and west directional lter 14 to a longitudinal circuit of the line wires. The field created by this longitudinal circuit west of the repeater point D creates a eld which is picked up by the receiving apparatus of train 68. Also, this energy of the longitudinal circuit is available at the terminal station W for effectively influencing the receiving apparatus RW at that station. The energy supplied to the longitudinal circuit at station E would create a field that would be available for effectively influencing the receiving apparatus on a train 15 operating between the repeater station C and the terminal station E.

At the transfer point CD a first Winding 16 of a transformer TI is connected across the line wires through blocking capacitors 11 and 18 andV a,l second winding 19 of the transformer TI is connected to the longitudinal circuit of the line wires through a connection including ground and capacitors 80 and 8l connected in series across the line wires. Thus a portion of the energy transmitted over the transverse circuit extending between repeater points C and D is fed through the winding 16 of transformer TI and energy is transferred to the longitudinal circuit, and the energy of this longitudinal circuit creates a field that will effectively influence the corresponding receiving apparatus of a train 88 operating somewhere between the points C and D. f

Thus the energy supplied at the terminal station E is available on a longitudinal circuit at all points along the division. r

I shall next assume the train 68 answers the communication from station E; -fTo do so, thev operator on the train 68 could use the transmitter which supplies the carrier current of they east frequency fe. Such energy supplied to the sending circuit of train 68 will be inductively trans-` y, ferred to the longitudinal circuit adjacent the train between station W and point D. This energy is passed through the circuit channel including east directional filter 82, amplifier 83 and east directional filter 84 and the amplified output is applied to the. transverse circuit east from repeater point D. At repeater point C the energy from the transverse circuit is passed through the circuit channel including east directional filter 85, amplifier 86 and east directional lter 81 to the longitudinal circuit extending east from repeater point C. Energy from this longitudinal circuit will be received at station E through the east lter EF and the corresponding receiver RE.

In the case the train 88 desires to transmit to station E, the operator on train 88 would energize" the transmitter arranged to supply the carrier frequency fe and this energy could be inductively transferred to the longitudinal circuit.v At the point CD energy from the longitudinal circuit would be passed through transformer TI to the transverse circuit and energy from this transverse circuit would be passedv at repeater point C through the circuit channel including vfilters 85 and 81 and amplifier 86 to the longitudinal circuit extending east from repeater point C and current from this longitudinal circuit wouldv be' effectively received at the station E. Transmission from train 15 to station E would be through and station E, in the usual manner.

For the operator at terminal W to communicate with any of the trains 68, 15 or 88, he would use his transmitter TE to supply energy of the east carrier frequency to the longitudinal circuit and v such energy would create a eld which wouldV verse circuit. At repeater point C energy frorn the transverse circuit is passed through the circuit channel including filters 85 and 81 and amplifier 86 to the longitudinal circuit east of point tudinal circuit would effectively influence the corresponding receiver of train 88. A

Transmission from any of the trains 68,;15 and 881to' the west terminal station W is accomplished by use of the west carrier frequency fw, the energy being transferred at the repeater points in 'a' manner that will be readily understood by an inspection of Fig. 2 taken in connection with the description of the transfer of energy from the trains to the east terminal station E.

It is to be observed that in Fig. 2 the operator on train 68 can communicate with either train 88 or 15 by transmitting on the east carrier frequency and either train 15 or 88 can reply to train 68 by transmitting on the west carrier frequency. That is, each train can communicate with any other train on the division by proper use of the east and west carrier frequencies.

the longitudinal circuit between repeater point C C, and energy of this longitudinal circuit would be available to influence the corresponding receiver on train 15 and also to influence `theV rs Itfis also to .fbefobserved thatat .point CDithe transfer of energy from -the transverse to the Although I'have rherein shown Aand rdescribed but two forms of communication ysystems feno-- bodying myinvention, it is to bezunderstood that various changes and modications may bemade therein within the :scope of the appended claims without departing from the spirit and scope :of

myiinvention.

-Jllawiing "thus `described 'my invention, what I claim'is:

'tlf-'In 'a 'system for communication between :a

vehicle operating over a stretch of trackway and .afways'ide station, vthe combination rcomprising, -a pair of line wires extending Yalong th'estretch t'o @be Vinducti-Vely associated with communication equipment on the vehicle due to the line wiresl in parallel lwith their -distributed l capacitance to ground -formingra longitudinal circuitgsaid line wires adaptable of --being included in series in a transverse'iinecircuit,fmeans to couple communication fequipment fat said station to said line Wiresito:supplyenergy thereto, means at at least one-'preselectedrpoint along thestretch to sectionalizeisai'd iline rwires into a-plurality of sectionsI which: arelindependent ofeach other withrespect tovthe longitudinal and Lvtransverse circuits rfor said=communication energy, repeater -meansvat eachsaid sectionalizing point,said repeater means connected yto said line wires eachfside i of said s'ectio'nalizingrk means to transfer energy from the .line Wires formed asa transversecircuit tothe line Lwires "formed as-a longitudinal circuit land vice versa,\an`d other'transfer means located at pcintsof selected ones of said sections and connectedtofsaid line wires to transfercsaidfcommunication energy of the'iongitudinal-line vcircuit toitheltransverse line circuit ofthe section and viceversa,` said transferl of energy by saidA repeater and'transfer means providing effective communication between said station and said-vehicle throughout said stretch.

i12.' 'lInP-a system for two-way communication: betweentabvehicle operating` over a division of track- Wayland a fterminalstationat one Aend ofthel division, `the combination comprising, f a pair of line wires extending -along the trackway 1tobe inductively-asscci-atediwith circuit elements carriedfoni said vehicle due to the longitudinal?cir` cuit formed by said line wires inparallel'and theindistributed capacitance and conductance'to ground, I`:said line wires in series adaptable of beingfincluded in-a transverse line circuit, communication equipment on the vehicleconnected` toV-'saidscircuit elements to transfer communica tion: 'energyr-to and from .theV longitudinal circuit,- other =1com=munication equipment at said station coupled tov thezline wires tov-transferk communicationfenergytoband from the transverse circuit'of theoline wiresflalplurality of repeater equipmentsI each including. amplifyingmeans and located onei atlreachoffza plurality of. preselectedy pointsialon'g said division, andfsaid'station and repeater vequipmentscconnected tosaid line WirestOsuppIy the communicationienergy to longitudinal ,circuitszof theiline wiresicntheeentire portion lofzthe division cricommuncation.withrlthetyehicle :at all points along ithe ftraclswayfand-:toasupply fsilchinelfgfyfft transverse -circuits, of the line wires ,for miese.

lected portions of the division for v transmission ofithe communication energy.

1:3. rIn arsystem ,for :two-waycommunicationfbee tweenvehicles operating over `a divisiomofitrackway anda terminalstation at one endofthe division, the combination v comprising, a apair L@of line wires f extending along `said trackway to fbe, inductively ;-associated with circuit velementscar-A ried on said vehicles due to the longitudinal circuit-:formed by the line -wires in parallel andtheir distributed capacitance and conductance,

to fground, :said line wires in series adaptable of being included 2in a ftransverse -line circuit, coinmun'ication equipment -on ,each Vehicle operable toatransmitfon aiirst 4carrier `frequency and re-4 ceive on a Ysecond carrier frequency and each suclifequipment connected to said circuitelemellts offthe same ,vehicle l to Vtransfer-such-,enerefyt;to` andyfrom said longitudinal circuitother com` municatigon equipment at said-station operable tcitransmit onasaidgsecond carrier frequency ,and

l'fo ;reoeiv.,el on: said:firstcarrierfrequencyandfhav- 1 ing connections iwith ,said .line wires, repeater such c ommunicationfwenergy `from the longitua dinal `circuit to ithe` transverse circuit and said second channel =to :transfer the energy from t the` transverse .circuit tto the longitudinal circuit.

c4. :In aisystemjortwo-wayI communicationrbei tween lvehicles operating over-a divisionmf'trackf way and a terminal station at one end of the division, the 'combination comprising, zaiparrof. line i wires extending along said Agtraclsway :'-to be, inductively associated withA circuitv elementsccar-1l riedeon f ,said-:vehicles due ;to the longitudinal` circuitcformed by vfthe line fwires -in parallel and ltheir distributed capacitance to groundfcomrnuf nication VAequipment i on each vehicleoperable; to

transmit :on a first n carrier frequency and; receive on `a :second 'carrier frequencyfaind each suchf. eiquipment connected toaid circuiti elements fof f the same 'vehicle r, toftransfer-suchvenergyt to and from said longitudinal circuit, other :communication yequipment at said station operable `to y transmitcon saidnsecondcarrier, frequency-andthe; receive ronsaid rstl carrier frequency `and haw-.-

ingsconnections with.` a ytransverse circuit including said. line wires in series, faplurality oft-ire# peater equipments one--at each of-a pluralityl of preselected points along ylthe division eac-h such repeater equipmentincluding two circuit chan-4 nels oneof which' is eiiectiveto amplify andpassV energy'of said "rst carrier v'frequency in one directionand the other of which channels is efiective, to ampliiyl and pass ,energyy of said Second` carrier` frequencyiin the opposite direction,eachf, said repeater equipment connected tosaidg-lineto;.transfereenergyffrom; a longitudinal `circuitrto,

ajtransverse circuit "of :the line xwires and the other onel of vitstchannels to transfer energy; from liriewires to transfer energy from the longitudinal to' the' transverse line circuit and vice versa.

f 5`. In a system for communication between a Vehicle operating over a division of trackway and a terminal station located at one end of the division, the combination comprising, a pair of line wires extending through the division within effective inductive range of the trackway, a ve'- hicle circuit element disposed to inductively pick up-v communication current from a longitudinal circuit formed by said line wires in parallel and their distributed capacitance to ground, a vehicley carried receiver connected .to said circuit element and responsive to such communication current, a terminal station transmitter connected across said line wires to supply such communication current to a transverse circuit of said line wires, repeater equipment including an amplifier at each of three spaced points along the division; and Vsaid repeater equipments connected to the line wires for a rst one to transfer said current from'the transverse circuit to the longitudinal circuiti,` a second one to transfer the current from the longitudinal circuit to the transverse circuit and a third one to transfer the current from the transverse circuit to the longitudinal circuit.

6. In a system for communication between vehicles en route over a trackway division and terminal stations located one at each end of the division', the combination comprising, a pair of line wires extending through the division within effective inductive range of the trackway, circuit elements mounted on each said vehicle for inductive relationship to a -longitudinal circuit of the line wires, communication equipment at each of `said stations having a transmitter to supply current of a first carrier frequency and a receiver responsive to current of a second carrier frequency, other communication equipments one-on each of said vehicles and having a transmitter to supply current of said second carrier frequency and a receiver responsive to current of said first carrier frequency, each said vehicle transmitter and receiver connected to the circuitv element of the same vehicle for inductive transfer of energy to and from the longitudinal circuit,

each said station transmitter and receiver con-A each said repeater equipmenthavingtwo circuit channels each including an amplifier and a filter,

a first one of said channels disposed to pass said r'st carrier frequency and a second one of said channels disposed to pass said second carrier frequency, and each said repeater equipment connected to said line wires for a, preselected one of its channels to transfer energy from the the transverse circuit to the longitudinal circuit and its other channel to transfer energy from the longitudinal circuit to the transverse circuit.

7. In a system for communication between vehicles en route over a trackway division and terminal stations located one at each end of the division, the combination comprising, a pair of line wires extending through the division within effective inductive range of the trackway, com. munication equipment at each of said stations operable to send on a first carrier frequency and to receive on a second carrier frequency, each said station equipment connected across said line wires to send and receive through a transverse circuit of the line wires, otherA communication equipment on each of said vehicles 'operable to send on said second carrier frequency and to -lr'ef ceive fon said first carrier frequency, each sai`dye'`7 hicle' equipment connected to circuit elements v`to?A inductively send and receive through a longitudi nal circuit of the line wires, repeater equipment located atflve points spaced to divide said tracks-'f way into six substantially equal sections, each said.,l repeater equipment having two Icircuit channelsi one ofxwhich includes an amplifier and a filter to; pass said first carrier frequency and the other-ini.'-y cluding. an amplifier and a filter to pass said second carrier frequency; said first, thirdand'fthi repeater equipmentsy connected to said line wires" for their first circuit channel to transfer energy, from 'the transverse to the longitudinal circuitand the second circuit channel to transfer energy from the longitudinal to the transverse circuit;V and said second and fourth repeater equipments connected to the line wires for their first circuity channel to transfer energy from the longitudinal to the transverse circuit and the second circuitichannel to transfer energy from the transverse to theA longitudinalA circuit.

8.'In a system for communication betweenI vehicles enroute over a traokway division andl terminall stations one at each end of the divisionY the combination comprising, a pair of line wires extending through the division in effective induc-` tive range of the trackway, communication equip7| ment at each of said stations operable to transmit communication currents each using an individual, carrier frequency of a rst group of carriers and, to receive communication currents each using anindividual carrier frequency of a second groupl of carriers, each said station equipment connected? to said line wires to send and receive on a trans--A4 verse circuit of the line wires, communication, equipments on each of vsaid vehicles operablento' transmit communication currents each using an. individual carrier of said second group of carriers; and-to receive communication currents each using; an individual carrier of said first group of car-` riers, each said Vehicle equipment connected to circuit elements inductively associated with ,al longitudinal circuit of said line wires, repeater;- equipments located one at each of a plurality'off preselected points along the division and eachI having two circuit channels one to pass only said, first group of carriers and the other to pass only,

said second group of carriers, and said repeater;l

equipments connected to said line wire to transfer energy from the transverse circuit to the longi-.5 tudinal circuit, as required to provide a plurality.' of conversations simultaneously between each station and vehicles in a preselected portion of the` division adjacent the station and between loothv stations and vehicles in a given overlap portion of the division. f

9. In a system for communication between, vehicles en route over a trackway division and terminal stations one at each end of the division,;. the combination comprising, a pair of line ,wiresi extending through the division in effective ine.; ductive range of the trackway, said stations have: ing communication equipments for the equip ment at a first one of the stations to send on a first carrier frequency and receive on a second' carrier frequency and the equipment at a second; one of the stations to send on said second carrier frequency and receive on said rst carrier fre-` quency, each said station equipment connectedto said line wires formed as a longitudinal circuit including said line wires in parallel and their dis-` tributed capacitance to ground, each said vehicle;l

7| having communication equipment to send and-ref` i7" ceive on either of said carrier frequencies', and circuit elements on each of `said vehicles connected to the vehicle equipment and mounted for inductive relationship with the longitudinalv circuit of said line Wires.

10. In a system for communication between vehicles en route over a trackway division and terminal stations one at each end ofthe division, the combination comprising, a pair of line Wires extending through the division in effectivei'inductive range of the trackway, said stations hav ing communication equipments for the equipment at a rst one of the stations to send on a first carrier frequency and receive on a Second carrier frequency and the equipment at a second. one of the stations to send on said second carrierfrequency and receive on said first carrier frequency, each said station equipment connected to said line wires formed as alongitudinal circuit including said line wires in parallel and their distributed capacitance to ground, each said vehicle having communication equipment to send and receive on either of said carrier frequencies, circuit elements on each of said vehicles connected to the vehicle equipment and mounted for inductive relationship with the longitudinal circuit of said line wires, repeater equipment including a first and a second circuit channel at two points along the division and connected to the line wires to transfer energy from the longitudinal circuit to a transverse circuit, said rst and second circuit channels including filters to pass said rst and second carrier frequencies respectively, and transfer equipment intermediate said two repeater points and including a transformer connected to said line wires to transfer energy from said transverse circuit to a longitudinal circuit and vice versa.

11. In a system for communication between vehicles en route over a trackway division and east and west terminal stations of the division, the combination comprising, a pair of line wires extending between said stations to be continuously within effective inductive range of the trackway, said east terminal station having communication equipment to send on a west carrier frequency and receive on an east carrier frequency, said west terminal station having com munication equipment to send on said east carrier frequency and receive on said West carrier frequency, each said station equipment connected to said line wires formed as a longitudinal circuit including said line wires in parallel and their distributed capacitance to ground, communication equipment on each said vehicle and each operable to send and receive on both said carrier frequencies, each said vehicle equipment inductively associated with the line wires formed in a longitudinal circuit, an east repeater equipment connected to the line wires to transfer said west carrier from the longitudinal to a transverse circuit and said east carrier from the transverse to the longitudinal circuit, a west repeater equipment connected to the line wires to transfer said east carrier from the longitudinal to the transverse circuit and said west carrier from the transverse to the longitudinal circuit, and transfer equipment intermediate said repeater equipments connected to the line wires to transfer either carrier from the transverse to the longitudinal circuit and vice versa.

12. In combination, a stretch of trackway, a vehicle to travel said trackway, a pair of line wires extending along said stretch within effective inductive range of said trackway, communication l8` equipmenton said vehicle operable to supply and to respond to carrier frequency currents and connected to circuit elements inductively associated with said line wires due to the longitudinal circuit formed by the line wires in parallel and their distributed capacitance to ground, a wayside station, communication equipment at said station operable to supply and to respond to said carrier frequency currents and having connections across said line wires at one end of said stretch to transfer such current to and from a transverse circuit of the line wires, and transfer means including a transformer located at an intermediate point of said stretch and having one winding connected to the transverse circuit of said line wires and a second Winding connected to the longitudinal circuit of the line wires.

.13. In a system for communication between vehicles en route over a trackway division and a terminal station at one end of the division, the combination comprising, a pair of line wires extending4 along the division in effective inductive' range of the trackway, said station having communication equipment to send on a first carrier 'l frequency and to receive on a second carrier frequency, said station equipment connected to a longitudinal circuit formed by said line wires in parallel and their distributed capacitance to ground, said line wires in series adaptable of being included in a transverse circuit, each said vehicle having communication equipment to send and receive on said second and rst carrier frequencies respectively, circuit elements on each of said vehicles connected to the vehicle equipment and mounted for inductive relationship with a longitudinal circuit of said line wires, repeater equipment at a point along the division spaced from said station and including a first and a second circuit channel, said first circuit channel adapted to pass only said first carrier frequency and connected to the line wires to transfer energy from the longitudinal circuit to the transverse circuit, said second circuit channel adapted to pass only said second carrier frequency and connected to the line wires to transfer energy from the transverse circuit to the longitudinal circuit, and transfer means located along the division spaced more remote from the station than said repeater point and including a transformer connected to said line wires to transfer energy from the transverse circuit to the longitudinal circuit and vice versa.

14. In a system for communication between a vehicle operating over a given stretch of trackway and a wayside station, a pair of line wires extending along said trackway, said line wires adaptable of being used in a longitudinal circuit formed by the line Wires in parallel and their distributed capacitance to ground and in a transverse circuit including the wires in series, said line wires extending along said trackway for inductive relation between the longitudinal line circuit of the wires and equipment supplying a given communication energy mounted on said vehicle, other equipment supplying said communication energy located at said station and having connections to said line wires, means at at least one preselected point along said stretch interposed in said line wires to sectionalize the wires into a plurality of different sections with respect to said longitudinal and transverse line circuits for said communication energy, repeater means including an amplifier at each of said sectionalizing pointsand connected to said line wires on each side of the sectionalizing means to transfer said communication energy from a longitudinal cir-,-

cuit of the line wires on one side of said means to a transverse circuit of the line wires on the other side of said means and vice versa, and other transfer means for designated ones of said sections connected to the line wires to transfer said communication energy from -the transverse line circuit to the longitudinal line circuit and vice versa.

15. In a system for communication between a vehicle operating over a given stretch of trackway and terminal stations one for each end of said stretch, the combination comprising, a pair of line wires extending between said stations and disposed along the trackway for inductive relation with circuit elements carried on said vehicle, said line wires adaptable of being used in a transverse line circuit and in a longitudinal line circuit, communication apparatus carried on said vehicle connected to said circuit elements for inductive transfer of communication current to and from said longitudinal line circuit, other communication apparatus at each of said stations coupled to said line wires to supply energy thereto but which energy is suiiicient to provide communication with the vehicle only for a given distance from the respective station and which distance is less than the length of said stretch, means interposed in said line wires at spaced points along the stretch to sectionalize the line wires into at least three sections with the end sections adjacent said stations each not greater than said given distance and the intermediate section not greater than twice said given distance, repeater means including amplier means at each of said sectionalizing points and connected to said line wires on each side of the sectionalizing means to transfer said communication current from the transverse to the longitudinal line circuit and vice versa, and other transfer means for said intermediate section connected to said line wires at substantially the mid point of that section to transfer said communication current from the transverse to the longitudinal line circuit and vice versa.

PAUL N. BOSSART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,453,387 Espenschied et al. May 1, 1923 1,803,453 Aiel May 5, 1931 

